Compounds or proteins that interact with tubulin will often alter one or more of the characteristic phases of polymerization. For example, Figure 2 shows the effect of adding the anti-mitotic drug paclitaxel to the standard polymerization reaction. A 3 μM concentration of paclitaxel eliminates the nucleation phase and enhances the Vmax of the growth phase. Thus, one application of this assay is the identification of novel anti-mitotics. Figure 1 also shows the effect of adding the microtubule destabilizing drug, vinblastine. At 3 μM final concentration, vinblastine causes a drastic decrease in Vmax and reduction in final polymer mass.

Figure 2. Tubulin polymerization using the fluorescence based tubulin polymerization assay (BK011). Tubulin was incubated alone (Control), with Paclitaxel or Vinblastine. Each condition was tested in duplicate. Polymerization was measured by excitation at 360 nm and emission at 420 nm. The three Phases of tubulin polymerization are marked for the control polymerization curve; I: nucleation, II: growth, III: steady state equillibrium.